Placed images resizing on their own in AI CC 2017

Wondering if anyone else has had this experience.

I am using Adobe illustrator CC 2017 on an iMac (Retina 5K, 27-inch, Late 2015), running Sierra 10.12.1. Whenever I open a client file with placed images in it, Illustrator automatically resizes the placed images to a random percentage. If I delete the image and re-place it, I then get a tall, vertical box with my image taking up just a fraction of the height of the box, justified to the bottom. The remainder of the image box is blank.

This happens no matter what image I place, no matter what its physical size, resolution, color mode, etc.

Screen shot included for reference. ANY help is appreciated.